(1) Field of the Invention
The subject of this invention is a rotary pump of the type using vanes. More in detail, this invention concerns a rotary pump of the type comprising a stator, in this stator a chamber delimited by a peripheral wall, formed in said stator an inlet connection and an exit passageway, an inlet passageway formed in said stator and extending from said inlet connection to said chamber, within said chamber a rotor, mounted revolving around an axis eccentric with respect to said chamber, said rotor having a support portion, a vane supporting portion and mechanical coupling means intended for driving the rotor in rotation, said vane supporting portion of the rotor being tangent to a region of the peripheral wall of said chamber, said vane supporting portion of the rotor having two parallel walls that delimit a diametrical space and divide the vane supporting portion in two half shells, and at least one vane, mounted sliding in said diametrical space of the vane supporting portion and tangent at its end portions to the peripheral wall of said chamber.
(2) Description of Related Art
Several vane pumps of the above mentioned type are known, and they may have a single vane inserted in said diametrical space of the rotor, said single vane cooperating with opposite portions of the peripheral wall of said chamber, which in this case should have a special outline similar to an ellipse and therefore is usually described as ellipsoidal. Otherwise, these pumps may have two vanes inserted in said diametrical space of the rotor, extending in mutual continuation and cooperating with opposite portions of the peripheral wall of said chamber, which in this case may have a circular outline.
In every case, the single vane or the two vanes and the tangency of the rotor to the peripheral wall of the chamber subdivide the pump chamber by defining therein a suction chamber and a compression chamber, and the rotation of rotor causes a periodical volume modification of said suction and compression chambers. When the rotation of rotor is driven in a suitable sense, it causes a suction from the inlet connection and a delivery from the exit passageway. A rotation of the rotor in the opposite sense would cause an inversion of these operations. To the inner space of pump is supplied oil having the double function of lubricating and of improving the pneumatic sealing of the component parts having a relative movement.
These pumps are widely used in several technical fields, and an application very extended of them is for producing a depression in a reservoir, such depression being used for operating some apparatuses. These pumps are defined vacuum pumps, and they are provided with a one-way valve controlling the suction passageway. In the field of motor vehicles, such vacuum pumps are driven by a cam shaft of the engine, or by another engine driven shaft, and they are especially used for operating the servo systems for the assisted braking, and other pneumatic effectors. In view of the prevailing character of this use, the same will be considered in the following description, being however understood that the described pump can be used for several other applications in the field of motor vehicles as well as in other technical fields.
In the known embodiments, these pumps give satisfactory performances, however they have some drawbacks. Particularly, the pump cannot be driven in the sense opposite the prescribed sense without inverting its operation. Therefore it is needed that differently designed pumps are manufactured, in order to satisfy the requirements for operating the same in opposite senses. Moreover, heavy consequences may take place if a vacuum pump is driven in the sense opposite the prescribed sense, as it may happen when the vehicle engine is subjected to a counter rotation. In this case overload are produced, that may cause the breaking of some component parts.
In the region of tangency between the rotor and the peripheral wall of the chamber, generally is formed a dead space which causes a reduction in the performances and an increase in the power required for operating the pump. The pump needs that a discharge valve is installed, which renders more complicated the installation of the pump on the engine. Also, the supply to the pump of the oil intended to lubricating the component parts thereof involves some difficulties.